1. Field of the Invention
The present invention relates to methods of coating a catalyst carrier layer of metal-metal oxide and depositing a catalyst on metal substrates for preparation of metal monolith catalyst modules, and monolith modules prepared using the metal substrate having the deposited catalyst. More specifically, the present invention relates to a method of forming a porous particle layer of metal-metal oxide as a catalyst carrier by coating on a metal substrate for subsequent easy deposition of catalyst particles upon preparation of a monolith type (honeycomb) catalyst module useful as a catalytic reactor with low pressure drop; a method of depositing an active catalyst component on the porous layer of metal-metal oxide; and a monolith module useful as a catalytic reactor with low pressure drop prepared using the metal substrate having the deposited catalyst.
2. Description of the Prior Art
In case of removing pollutants, such as hydrocarbons, NOx, volatile organic compounds (hereinafter, abbreviated to ‘VOC’), dioxin, etc., in autoexhaust discharged from incinerators, stacks or automobiles through catalytic oxidation, or in case of performing a catalyst reforming process of hydrocarbons or alcohols used in small fuel cells or catalytic combustion devices of fuels including methane, there is required a specific support capable of dispersing catalyst particles to decrease pressure loss in reactors.
As the support functioning for dispersing-depositing of catalyst particles upon performing low pressure drop reaction, a monolith module has been widely used. In this regard, there are provided reactors suitable for use in removal of hydrocarbons, NOx, VOC contained in exhaust gas discharged from the stacks by chemical reaction, or honeycomb reactors for treatment of automobile exhaust gas (Catalysis Review-Sci, and Eng., 36(2), 179–270, 1994).
In particular, in the reactors mentioned above, the ceramic honeycomb reactor was developed in the early 1970s and is still used generally. In U.S. Pat. Nos. 3,785,781, 4,072,471, 4,814,146 and 5,547,641, there are disclosed a reaction process performed using a honeycomb reactor and an installation method of the reactor. Further, in U.S. Pat. Nos. 3,991,245, 4,824,711, 5,145,825, 5,290,739, 5,376,610, 5,681,788 and 5,938,992, there are mainly disclosed a honeycomb module, an optimized catalyst material and a preparation method thereof.
However, the ceramic honeycomb reactor, which is generally used, is disadvantageous in terms of non-uniform flow distribution due to unidirectional channels and a closed structure between channels, slow diffusion rate of reactants to the catalyst's surface due to low turbulence in channels, and unnecessarily large reactor. Further, in case of wash-coating catalyst particles into the channels, the catalyst particles are not uniformly deposited and are mainly deposited to corners of square shaped channels in the reactor, thus decreasing catalytic activity. Also, the reactor having low thermal conductivity is unfavorable upon requiring fast temperature response characteristic in reactors, such as automobile autoexhaust treatment or fuel cells, and further is difficult to form in various shapes due to complex processes of extruding and molding ceramic materials.
In order to solve the problems, Korean Patent Laid-open Publication No. 2001–951 discloses a 3D-honeycomb module using a metal mesh. The 3D-honeycomb module made of metal mesh has advantages, such as high thermal conductivity, larger surface area per unit volume of the module, easy preparation, and having uniformly deposited catalyst particles. The flux flows in a channel direction as well as a direction perpendicular to channels and thus turbulent flow is formed, resulting in high mass transfer rate. Consequently, the reactor volume is decreased.
However, in case of depositing the catalyst onto a wire surface of the metal mesh instead of the ceramic honeycomb module, problems are caused, such as low deposition strength, use of large amounts of binder, and decreased activity. Hence, upon depositing the catalyst onto the metal surface of the metal mesh wire, there is an urgent need for a method of depositing catalyst particles having a high surface area with high deposition strength and stability.